Many modern devices for displaying video, such as high-definition televisions, computer monitors, and cellular telephone display screens, allow users to manipulate the displayed video by zooming. In traditional systems for zooming video, the displayed resolution of the video decreases as the zoom factor increases. This decreased resolution can result in pixelization effects that cause a zoomed video to appear blurry. Blurriness increases with the zoom factor, preventing a user from being able to view details of the zoomed video and resulting in an unpleasant viewing experience.
Users also may desire to pan the displayed video. A combination of zoom and pan commands would allow a user to focus in on a selected portion of the video. The selected portion of the video sometimes is referred to as the display window.
Traditional methods and systems, however, may require a user to download and decode bitstreams corresponding to entire video frames, even though the user is only viewing the portion of the frames within the display window, as specified by zoom and pan commands. Unnecessary downloading and decoding of entire frames is an inefficient use of bandwidth and computational power.
Accordingly, there is a need for video encoders and for video distribution systems that provide multiple levels of resolution depending on the zoom factor. There also is a need for systems of providing and displaying video that provide, decode, and display only the portions of video frames within the display window.